Generally, a copper line layer is used as a line layer in semiconductor devices. However, the copper line layer is difficult to pattern, so a damascene process is usually used to form the copper line layer.
FIG. 1 and FIG. 2 are cross-sectional views illustrating a conventional method for forming a copper line layer in a semiconductor device.
Referring to FIG. 1, in the conventional method for forming a copper line layer in a semiconductor device, a damascene insulating layer 105 having contact holes 110 and 115 is formed on a silicon substrate 100. A tantalum nitride (TaN) layer and a tantalum (Ta) layer are sequentially formed in the contact holes 110 and 115 of the damascene insulating layer 105, and thus, a barrier metal layer 120 is formed therein. Subsequently, a seed copper layer 125 is formed on the barrier metal layer 120.
Referring to FIG. 2, a copper line layer 130 is formed on a seed copper layer 125a so as to fill the contact holes. To form such a copper line layer 130, a copper layer is first formed to sufficiently fill the contact holes 110 and 115. Then, a chemical mechanical polishing process is performed to form a barrier metal layer 120a and the seed copper layer 125a confined in the contact holes 110 and 115. FIG. 2 shows the seed copper layer 125a separately, but it should be understood that it may be included in the copper line layer 130.
In the conventional method of FIGS. 1-2, a contact characteristic of the barrier metal layer with the silicon substrate or the damascene insulating layer is degraded because the tantalum nitride (TaN) layer of the barrier metal layer directly contacts the damascene insulating layer. In addition, although a pure copper (Cu) line layer has a relatively better electromigration (EM) characteristic than aluminum (Al) due to its heavier weight, it is understood that such a relative merit is not sufficient. Therefore, the reliability of such a device may also become deteriorated if it is used for a long time.
To clarify multiple layers and regions, the thickness of the layers are enlarged in the drawings. Wherever possible, the same reference numbers will be used throughout the drawing(s) and accompanying written description to refer to the same or like parts. As used in this patent, stating that any part (e.g., a layer, film, area, or plate) is in any way positioned on (e.g., positioned on, located on, disposed on, or formed on, etc.) another part, means that the referenced part is either in contact with the other part, or that the referenced part is above the other part with one or more intermediate part(s) located therebetween. Stating that any part is in contact with another part means that there is no intermediate part between the two parts.